Hi,
I discovered Previous this week-end after discussing about a NeXT workstation someone brought to a local retro event.
I tried to build the latest branch (branch_realtime) but it failed to display anything in the window...
I ended up git bisecting the repo until 4am, and found it worked on r585, next dozen revs failed to build, while the next revision that actually compiled had a broken display.
The culprit is SDL_CreateRenderer() is now being called from a different thread than the one that actually calls SDL_RenderPresent().
It seems that those should actually only be called from the main thread anyway, but at least it works this way.
(I'm on Debian Sid)

Thank you for the patch. I extended it to the NeXTdimension repaint thread and applied it to the repository. Please test the latest revision (r642) or branch_realtime. It would be interesting for me, if the NeXTdimension screen also repaints correctly now.